1. FIELD OF THE INVENTION
This invention relates generally to hypodermic injection devices and more particularly to a needleless hypodermic injector ampule which can be charged with a medicant immediately prior to its use.
2. PRIOR ART
Application for U.S. Pat. Ser. No. 342,508, which is the parent application to this application, discusses some of the prior art pertaining to needleless hypodermic injection and some of the disadvantages associated therewith. That application discloses and claims a disposable needleless injector which employs a medicant containing ampule formed of a suitable material, such as stainless steel, which is inert with respect to the medicant contained therein. It can be readily appreciated that the use of stainless steel to form a medicant containing ampule is relatively expensive, particularly if the ampule is of the disposable type.
However, the use of relatively inexpensive materials results in other disadvantages. The major problem encountered in thee use of inexpensive materials is the prolonged storage of medicants. That is, many of the inexpensive materials which are suitable for the fabrication of an ampule interact over extended periods of time with thee majority of medicants which may be contained in such an ampule. Plastics are of this character. Other inexpensive materials are not suitable for the fabrication of ampules for one or more reasons. The U.S. Food and Drug Administration requires the prolonged storage of medicants in either glass or rubber containers. However, glass is fragile and, therefore, is not a desirable medicant container, particularly as an ampule in a needleless injector, since it must be able to withstand internal pressures during an injection. The yieldability of rubber makes its unsuitable, since it must be reinforced before it can be used under pressurized conditions which exist during a needleless injection with the device.
If it is feasible to fill an ampule immediately prior to its use, some of the relatively inexpensive materials are acceptable, since the medicant does not have an opportunity to interact with the containing material. Plastics and aluminum have all of the qualities which are desirable, such as rigidity, if the ampule is filled with the medicant immediately prior to its use.
It has been the practice in the past to supply a user with a large number of prefilled ampules, each containing a specified medicant. If a particular medicant is not used specifically in needleless injections, it may become stale and may have to be discarded after a period of time. On the other hand, if a medicant is used extensively for needleless injectionn and all of the prefilled ampules containing that medicant have been used, the user cannot refill such ampules from a larger supply. It can be appreciated, therefore, that a need exists for a medicant ampule for use in a needleless injector which can be filled immediately prior to its use quickly and easily by the user.